Composition of Wellbore Cleaning Agent

ABSTRACT

A cleaning agent, which comprises a mutual solvent, a carrier fluid, a nonionic surfactant and another nonionic surfactant as co-surfactant. The cleaning agent can be used, for example, to clean oil and water based drilling mud and water-wet the surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/095,129, filed Dec. 22, 2014.

BACKGROUND OF INVENTION

1) Field of the Invention

This invention relates to the formulation of a cleaning agent which iscapable of cleaning wellbore and water-wet the surface.

2) Background Information

Various fluids, including oil based mud (OBM), synthetic oil based mud(SBM) and/or water based mud (WBM), were applied during the wellboredrilling process for the exploration and/or production of fossil fuel.During drilling, mud is circulated continuously and leaves the wellboresurface and other surfaces contaminated. Effective drilling mud removalis a necessary for both cementing success and completion operations.Before cementing, the casing and formation need to be water-wet so thatcement can bond with both casing and formation. Before completion of awell, it is necessary to displace the mud and water-wet the casing,tubular so that clean fluid, typically clear solids-free brine, can beplaced into the well. Conventional cleaning methods use fresh water orseawater treated with cleaning agents to displace the mud and water-wetthe surfaces. This low-density treating fluid creates a negativedifferential pressure between the working fluid and the formation, whichfrequently require unacceptable pump pressure. Weighed spacers orcleaning fluids can overcome the differential pressure problem. Aweighted spacer generally composes of a viscosifier, weighting material,and cleaning agent. Xanthan gum and other water-soluble polysaccharidesare frequently used as viscosifier. Barite, calcium carbonate and otherssolid material are frequently used as weighting material. Heavy weightbrine can be used as weighting material as well. However, the weightedcleaning fluids generally have limitation on the cleaning efficiency.

Accordingly, there is a demand for highly effective cleaning agents thatcan be applied in displacement spacers to remove mud residue and leavethe surface clean and water-wet.

SUMMARY OF INVENTION

The present invention provides an improved surfactant blend,particularly useful in well cleanout, cementing, well completion, inconnection with the exploration and production of oil and gas. Thisspecific surfactant blend is stable over a wide range of temperature andcan be mixed with any type of aqueous fluids including brine.

DETAILED DESCRIPTION

Embodiments disclosed herein relate to fluids used in cleaning wellboresurface including casing, tubular, and drilling pipe, as well asformation. More particularly, embodiments disclosed herein relate to useof fatty alcohol ethoxylates with specific value ofhydrophilic-lipophilic balance (HLB) to remove drilling fluid residue onwellbore surfaces and water-wet surfaces.

The HLB value of a surfactant is a measure of the degree to which it ishydrophilic or lipophilic. A HLB value of 0 corresponds to a completelyhydrophobic molecule, while a HLB value of 20 corresponds to acompletely hydrophilic molecule. HLB value can be used to predict thesurfactant properties of a molecule. For example, a surfactant with HLBvalue of 3 to 6 is W/O (water in oil) emulsifier. A surfactant with HLBvalue of 12 to 16 is O/W (oil in water) emulsifier. Typical oil basedmud is invert oil emulsion mud or water in oil emulsion mud.

There are four types of surfactants, including anionic surfactants,cationic surfactants, amphoteric surfactants in which the charge dependson pH, and nonionic surfactants. Nonionic surfactants are of particularinterest due to its stability in presence of ionic compound likemonovalent and/or divalent brines, largely used in oil and gas field. Itis contemplated that a cleaning agent having at least two surfactants,wherein the total surfactant concentration in the cleaning agent isabout 20% to 80% by weight and preferably 40% to 60% by weight. The HLBvalue of the first surfactant ranges from 6.0 to 12.0 and preferablyfrom 10.0 to 11.9. The HLB value of the second surfactant ranges from12.0 to 20.0 and preferably from 12.0 to 14.0. Both surfactants can beany of the four types of surfactants, wherein nonionic surfactant ispreferred. The weight ratio of the first surfactant to the secondsurfactant ranges from 1:0.1 to 1:10 and preferable from 1:0.5 to 1:2.Numerous surfactants fit the criteria. A few examples of surfactantshaving a HLB value ranging from 10.0 to 12.0 and from 12.0 to 15.0 arelisted in Table 1 and Table 2. Alcohol ethoxylates are a major class ofnon-ionic surfactants which are used in laundry detergents, householdand industrial cleaners, cosmetics, agriculture, and in textile, paper,oil and other process industries. The Alcohol ethoxylate is defined tobe of the basic structure Cx-yEn. The subscript following the ‘C’indicates the range of carbon chain units. Alcohol ethoxylates withcarbon unit range between C6 to C18 are most used. The carbon unit canbe aliphatic, alicyclic or aromatic. In other words, the carbon unit canbe straight or branched, cyclic or aromatic, saturated or unsaturatedand may contain carbon, oxygen, hydrogen, nitrogen, sulfur etc. Further,alcohol ethoxylates contain ethylene oxide (E) chain attached to thealcohol. The subscript following the ‘E’ indicates the degree ofpolymerization of ethylene oxide units. The performance properties ofthese non-ionic surfactants can be adjusted by the alcohol selection andby the length of the hydrophilic polyethylene glycol chain. The HLBvalues of those alcohol ethoxylates may vary accordingly. A nonionicsurfactant WC-100, is an ethoxylated alcohol having an alkyl chainlength of C6, which has a HLB value at about 11.8. Other nonionicsurfactants WC-102 and WC-104 are ethoxylated alcohol having an alkylchain length of C8-C16, which has a HLB value at about 13.1 and 12.1,respectively. Those surfactants meet the criteria to be the surfactantand the co-surfactant in the cleaning agent and are available fromWellbore Chemicals LLC.

TABLE 1 Examples of surfactants having a HLB value ranging from 10.0 to11.9 Surfactant HLB value PEG-7 glyceryl cocoate 10.0 PEG-20 almondglycerides 10.0 PEG-25 hydrogenated castor oil 10.8 C12-C14 alcoholethoxylates 4.5 mol 10.1 C12-C14 alcohol ethoxylates 5 mol 10.2 C12-C14alcohol ethoxylates 5 mol 10.5 PEG-100 stearate 11.0 Polysorbate 85 11.0PEG-7 olivate 11.0 Isotridecyl alcohol ethoxylate 6 mole 11.3 PEG-8oleate 11.6 WC-100 11.8

TABLE 2 Examples of Surfactants having a HLB value ranging from 12.0 to15.0 Surfactant HLB value Polyglyceryl-3 methyglucose distearate 12.0C10-C16 alcohol ethoxylate 6.5 mol 12.0 WC-104 12.1 Oleth-10 12.4Branched C13 alcohol ethoxylat 8 mol 12.7 Ceteth-10 12.9 PEG-8 laurate13.0 Nonylphenol ethoxylate 9 mol 13.1 WC-102 13.1 Hydrogenated castorOil ethoxylate 50 mol 13.5 C10-C16 alcohol ethoxylate 9 mol 13.5 Castoroil ethoxylate 60 mol 14.0 Polysorbate 60 14.9 Polysorbate 80 15.0

In addition to the surfactants, the cleaning agent may also contain atleast one mutual solvent. A mutual solvent is miscible with more thanone class of liquids. Acetone, for example, is miscible with water,alcohol, and ether. A mutual solvent is also known as a coupling agentbecause it can combine two ordinarily immiscible liquids togetherforming a clear solution. Examples of such solvents in the someembodiments include, but not limit to ethylene glycol monobutyl ether,diethylene glycol monobutyl ether, triethylene glycol monobutyl ether,propylene glycol monobutyl ether (PGMBE), dipropylene glycol monobutylether, tripropylene monobutyl ether, diethylene glycol monoethyl ether,dipropylene glycol monomethyl ether, butylcarbitol, various esters, suchas ethyl acetate, butyl acetate et al. In a particular embodiment, themutual solvent is ethylene glycol monobutyl ether (EGMBE) or its mixturewith other mutual solvents. In addition to the surfactants and mutualsolvents, the cleaning fluid may contain at least one carrier fluid,which is linear and/or branched alkyl alcohol. Examples of such carrierfluid in the some embodiments include, but not limit to, methanol,ethanol, n-propanol, isopropyl alcohol (IPA), butyl alcohol, pentanol,branched and linear hexanol, 2-ethylhexanol, 1-heptanol, 2-heptanol,octanol, alkyl alcohol C6 to C13 category, diols, for example,ethane-1,2-diol, propane-1,2-diol, propane-1,2,3-triol, prop-2-ene-1-ol,prop-2-in-1-ol et al. In a particular embodiment, the carrier fluid is2-ethylhexanol or its mixture with other alcohols. When the base fluidcomprises a blend of carrier fluid and mutual solvent, the blend mayinclude any ranges up to 1:4 by weight. In a preferred embodiment, theblend may range from 1:1 to 1:3 by weight. Further, when formulated withsurfactants, the cleaning agent comprises may include from 20% to 60% byweight of the based fluid and preferably 30% to 50% by weight. In aparticular embodiment, the cleaning fluid may include about 10 to 20% byweight of a carrier fluid, about 10 to 40% by weight of a mutualsolvent, and about 40 to 80% by weight of surfactants.

An oleaginous or aqueous fluid may be formulated into the cleaningfluids. The aqueous fluid may include at least one of fresh water,seawater, brine, mixtures of water and water-soluble organic compoundsand mixtures thereof. For example, the aqueous fluid may be formulatedwith mixtures of desired salts in fresh water. Such salts may include,but are not limited to metal halides, hydroxides, formates orcarboxylates, for example, the brine may include seawater, diluted seawater, In a particular embodiment, a brine may include halide orcarboxylate salts of mono- or divalent cations of metals, such assodium, potassium, cesium, calcium, and/or Zinc. Corrosion inhibitors,biocides, friction reducers and other oil field chemicals may also beformulated into the cleaning fluids.

EXAMPLE

The disclosure has been generally described. The following example isgiven to further illustrate the application and compositions of thepresent disclosure. In particular, the composition of various cleaningagents tested, which containing a carrier fluid, mutual solvent,surfactant and co-surfactant, have been listed in Table 3. All thechemicals are commercially available from chemical companies includingWellbore Chemicals LLC (Katy Tex.). Cleaning efficiency tests were basedon a conventional jar test. To a clean 4 OZ wide mouth glass bottle, 20ml oil based mud was added and the mud was swiveled to cover the innerwall of jar. In another 4 OZ glass bottle, 20 ml of the formulatedcleaning agent was mixed with 60 ml 11.6 ppg (sg 1.39) calcium chloridebrine to form an 80 ml cleaning fluid. The cleaning fluid was added intothe glass bottle that was covered by 20 ml oil based mud. After shakingfor 30 seconds, all the liquid was poured out and the bottle was rinsedusing tap water twice. The wall cleanness and wettability were observedand recorded. The cleaning efficiency was ranked from 0 to 10. A number0 indicates that mud was still attached to the wall and there is nocleaning efficiency. A number 10 indicates an excellent cleaningefficiency that yields a clean bottle without any mud residue and fullywater-wet. A cleaning efficiency should be numbered at least 8 to beconsidered acceptable.

TABLE 3A different surfactant and co-surfactant Sample No. ComponentFunction HLB 1 2 3 4 5 6 7 8 EGMBE Mutual 20 20 20 20 20 20 20 20solvent 2- Carrier 10 10 10 10 10 10 10 10 Ethylhexanol fluidIsotridecyl Surfactant 11.3 20 20 20 20 — — — — alcohol ethoxylate 6 molWC-100 Surfactant 11.8 — — — — 20 20 20 20 C10-C16 co-Surfactant 12.0 20— — — 20 — — — alcohol ethoxylate 6.5 mol WC-104 co-Surfactant 12.1 — 20— — — 20 — — Branched co-Surfactant 12.7 — — 20 — — — 20 — C13 alcoholethoxylat 8 mol WC-102 co-Surfactant 13.1 — — — 20 — — — 20 Cleaning  910  9  9 10 10  9  8 efficiency

TABLE 3B different mutual solvent and carrier fluid Sample No. ComponentFunction HLB 9 10 11 12 EGMBB — 10 10 — PGMBE Mutual solvent 20 10 10 15Isopropanol Carrier fluid 10 10 5 — 2-Ethylhexanol Carrier fluid — — 510 WC-100 Surfactant 11.8 20 20 20 25 WC-104 co-Surfactant 12.1 20 20 2020 Cleaning efficiency  8  9 10  9+

TABLE 3C mixture of surfactant and co-surfactant Sample No. ComponentFunction HLB 13 14 15 16 17 18 EGMBE Mutual 20 20 20 20 20 20 solvent2-Ethylhexanol Carrier 10 10 10 10 10 10 fluid Isotridecyl Surfactant11.3 — 20 10 10 10 5 alcohol ethoxylate 6 mol WC-100 Surfactant 11.8 20— 10 10 10 15 C10-C16 alcohol co-Surfactant 12.0 10 10 20 — 10 5ethoxylate 6.5 mol Branched C13 co-Surfactant 12.7 10 10 — 20 10 15alcohol ethoxylat 8 mol Cleaning  9+  9  9 10 10 10 efficiency

While limited numbers of embodiment of the invention have been shown anddescribed, modifications can be made by those skilled in the art withoutdeparting from the spirit and scope of the invention as recited inappended claims. The disclosures of all patents, patent applications,and publications cited herein are incorporated by reference, to theextent that they provide exemplary or other details supplementary tothose set forth herein.

REFERENCE

U.S. PATENT DOCUMENTS 8,584,760 B2 November 2013 Arvie et al 7,902,123B2 March 2011 Harrsion et al 6,672,388 B2 January 2004 McGregor et al5,458,197 October 1995 Chan

OTHER PUBLICATIONS

-   Milton J. Rosen; Surfactant and interfacial phenomena (3^(rd)    edition), 2004, John Wiley & Sons, Inc. Hoboken, N.J.

What is claimed:
 1. A wellbore cleaning agent comprising a mutualsolvent, a carrier fluid and a surfactant, and another surfactant as aco-surfactant.
 2. A wellbore cleaning agent composition as claimed inclaim 1 wherein the cleaning agent comprises a surfactant or a mixtureof surfactants, which have HLB value about 10.0 to about 11.9.
 3. Awellbore cleaning agent composition as claimed in claim 1 wherein thecleaning agent comprises a co-surfactant or a mixture of co-surfactants,which have HLB value about 12.0 to about 15.0.
 4. A wellbore cleaningagent composition as claimed in claim 1 wherein the cleaning agentcomprises a mutual solvent from the group of ethylene glycol monobutylether, propylene glycol monobutyl ether, ethylene glycol, propyleneglycol, derivatives thereof or combinations thereof.
 5. A wellborecleaning agent composition as claimed in claim 1 wherein the cleaningagent comprises a carrier fluid the group of isopropyl alcohol,n-propanol, n-butanol, tert-butanol, n-pentanol, n-hexanol,2-ethyl-hexanol, derivatives thereof or combinations thereof.
 6. Thecomposition of claim 2 wherein the surfactant comprises anionic,cationic zwitterionic and nonionic surfactant, or combinations thereof.7. The composition of claim 3 wherein the co-surfactant comprisesanionic, cationic zwitterionic and nonionic surfactant, or combinationsthereof.
 8. The composition of claim 2 wherein the nonionic surfactantscomprise alkylphenol ethoxylate, alcohol ethoxylate, polyoxypropyleneglycols, polyoxyethylenated mercaptans, fatty acid ester, sorbitolester, alkanolamides, tertiary acetylenic glycols, polyoxyethylenatedsilicones, alkylpolyglycosides, or combinations thereof.
 9. Thecomposition of claim 3 wherein the nonionic surfactants comprisealkylphenol ethoxylate, alcohol ethoxylate, polyoxypropylene glycols,polyoxyethylenated mercaptans, fatty acid ester, sorbitol ester,alkanolamides, tertiary acetylenic glycols, polyoxyethylenatedsilicones, alkylpolyglycosides, or combinations thereof.
 10. A wellborecleaning agent composition as claimed in claim 1 wherein cleaning agentcomprises from about 5% to 60% by weight of a mutual solvent, about 10%to 50% by weight of a surfactant, about 10% to 50% by weight of aco-surfactant and about 5% to 30% by weight of a carrier fluid.
 11. Awellbore cleaning agent composition as claimed in claim 1 wherein thecleaning agent comprises water or brine.
 12. A wellbore cleaning agentcomposition as claimed in claim 1 wherein the cleaning agent comprises aflocculating agent or mixtures thereof.
 13. A wellbore cleaning agentcomposition as claimed in claim 1 wherein the cleaning agent comprisesan organic solvent or a mixture of organic solvents.
 14. A wellborecleaning agent composition as claimed in claim 1 wherein the cleaningagent comprises a corrosion inhibitor or a mixture of corrosioninhibitors.
 15. A wellbore cleaning agent composition as claimed inclaim 1 wherein the cleaning agent comprises a weight agent or a mixturethereof.
 16. A wellbore cleaning agent composition as claimed in claim 1wherein the cleaning agent comprises a viscosifier or a mixture ofviscosifiers.